Predictive value of pretreatment metabolic activity measured by fluorodeoxyglucose positron emission tomography in patients with metastatic advanced gastric cancer: The maximal SUV of the stomach is a prognostic factor

Purpose: Few studies have evaluated metabolic activity by ¹⁸F-FDG PET as a prognostic factor in advanced gastric cancer (AGC). We investigated its prognostic role in metastatic AGC. Methods: We enrolled 82 patients with metastatic AGC, who were treatment-naive and underwent pretreatment ¹⁸F-FDG PET/CT scanning. In each patient, the maximal standardized uptake value (SUVmax) was measured in each target lesion. Stomach_SUVmax was defined as SUVmax in the stomach, while Total _SUVmax was defined as the highest SUVmax among all the target lesions. Results: The stomach was the organ most frequently displaying the highest SUVmax among all the target lesions (in 67.1 % of patients). A Total_SUVmax value of 11.5 was the value with the maximum sum of sensitivity and specificity from receiver-operating characteristic curves for progression-free survival (PFS). PFS was significantly longer in patients with a Total_SUVmax value <11.5 than in those with a Total _SUVmax value ≥11.5 (P=0.023); however, overall survival (OS) was not (P=0.055). A Stomach_SUVmax value of 6.0 was derived by similar methods. PFS and OS were significantly longer in those with a Stomach _SUVmax value <6.0 than in those with a Stomach_SUVmax value ≥6.0 (P=0.001 and P=0.006, respectively). Furthermore, those with a low Total_SUVmax and those with a low Stomach_SUVmax showed better chemotherapeutic responses (P=0.016 and P=0.034, respectively). Among patients with histologically undifferentiated carcinomas, those with lower Total_SUVmax and those with lower Stomach_SUVmax showed longer median PFS (P=0.027 and P=0.005, respectively) and OS (P=0.009 and P <0.001, respectively). Multivariate analysis demonstrated Stomach _SUVmax as an independent predictor of PFS (P=0.002) and OS (P=0.038). Conclusion: Pretreatment metabolic activity may be a useful prognostic marker in patients with metastatic AGC undergoing palliative chemotherapy. Notably, Stomach_SUVmax was the single, most robust factor predicting prognosis.